A Drug Screening Revealed Novel Potential Agents against Malignant Pleural Mesothelioma

Simple Summary Malignant pleural mesothelioma (MPM) is a disease of the pleura related to asbestos exposure. Despite the advancements in new therapeutic frontiers, it has a dismal prognosis and very limited treatment options. To find novel weapons in the care of MPM, we undertook a drug-repurposing approach that consists of evaluating existing drugs already approved for other human diseases. We screened 1170 drugs, and we observed that cephalomannine, a taxane; ouabain, a cardiac glycoside; thonzonium bromide, an antifungal surfactant; and emetine, an emetic alkaloid, had marked activity against immortalized and patient-derived primary MPM cell lines. These compounds were shown to be promising, and they will be evaluated in further studies, both in vitro and in vivo. We believe that drug repurposing is a valuable strategy to facilitate and accelerate the definition of novel treatment options for the management of MPM. The lack of effective therapies remains one of the main challenges for malignant pleural mesothelioma (MPM). In this perspective, drug repositioning could accelerate the identification of novel treatments. We screened 1170 FDA-approved drugs on a SV40-immortalized mesothelial (MeT-5A) and five MPM (Mero-14, Mero-25, IST-Mes2, NCI-H28 and MSTO-211H) cell lines. Biological assays were carried out for 41 drugs, showing the highest cytotoxicity and for whom there were a complete lack of published literature in MPM. Cytotoxicity and caspase activation were evaluated with commercially available kits and cell proliferation was assayed using MTT assay and by clonogenic activity with standard protocols. Moreover, the five most effective drugs were further evaluated on patient-derived primary MPM cell lines. The most active molecules were cephalomannine, ouabain, alexidine, thonzonium bromide, and emetine. Except for alexidine, these drugs inhibited the clonogenic ability and caspase activation in all cancer lines tested. The proliferation was inhibited also on an extended panel of cell lines, including primary MPM cells. Thus, we suggest that cephalomannine, ouabain, thonzonium bromide, and emetine could represent novel candidates to be repurposed for improving the arsenal of therapeutic weapons in the fight against MPM.